None
Not applicable.
This invention relates to dynamoelectric machines, and in particular, to a protective assembly for a start capacitor of an AC induction motor. While the invention is described with particular reference to its application in AC induction motors, those skilled in the art will recognize the wider applicability of the inventive principles disclosed hereinafter.
During the routine operating life of an AC induction motor, for example, one in which a capacitor is employed in the motor circuit, the capacitor, which is an electronic component, sometimes fails. When this occurs, the normal procedure is to: 1) remove electrical power from the machine; 2) remove the retaining screws or hardware that hold the capacitor in place on the machine; 3) disconnect the leads that provides the electrical energy to the capacitor; 4) remove the capacitor from the container holding the capacitor; 5) replace the capacitor with a new unit; 6) reconnect and reinstall the capacitor to the machine; and 7) reapply power to the machine. Unfortunately, this procedure is not always followed, and that failure has resulted in electrical trauma injury to users in the field. Current mechanical and electrical configurations commonly employed in dynamoelectric machine design permit the start and/or run capacitor to be connected electrically to the dynamoelectric machine without the capacitor being mechanically retained. Electrical connections often are not insulated. This permits contact of the capacitor terminals with the casing or shell of the motor and/or other metallic foreign objects. If the operator or user contacts the case or shell of the motor while the capacitor terminals is in contact with the case and power is applied to the motor, an electrical shock can occur.
In some known cases, individuals have removed start capacitors from their containers and disassembled them, exposing the electrical connections inside the capacitor. In several capacitor designs employed with induction motors, for example, the capacitor can be completely removed from its manufactured container and still function. When this occurs, the wires and contacts that carry electric power to the capacitor are exposed and can be directly contacted by the operator/user. Again, this has the potential to cause electrical trauma to a user.
As will be appreciated by those skilled in the art, if electrical power is disconnected from a capacitor it will retain charge for some period of time. Depending upon the capacitive value of the capacitor, the charge can be significant enough to cause shock trauma to a person who touches the leads of the capacitor. A high resistance resistor placed across the capacitor terminals will not effect operation of the capacitor in its intended application, and will provide a discharge path to drain the charge from the capacitor and reduce it to a point that will not injure a person who touches the leads.
It is also known that if an overcharge or over voltage condition exists in a capacitor, it can release gas from the materials forming the capacitor. These gases will build pressure inside the component until the capacitor explodes, unless the gases are vented. All capacitors manufactured in the United States have vent features to release these gases. The device disclosed hereinafter, while preventing tampering and protecting the electrical integrity of the system, provides a physical path to vent internal gases, should the capacitor be subject to an over voltage condition. While the potential for electric shock has been known in the past, the practical way to prevent it has been lacking. The invention disclosed hereinafter overcomes these prior deficiencies and provides a simple, low cost protective assembly particularly useful in dynamoelectric machine applications.
One of the objects of this invention is to provide an assembly that is intended to prevent electrical shock in dynamoelectric machine applications.
Another object of this invention is to provide a module, which prevents individuals from accessing a capacitor, mounted within the module without totally destroying the capacitor and its functionality.
Another object of this invention is to provide a bleed resistor for capacitors utilized with dynamoelectric machines.
Another object of this invention is to provide a module that protects an individual from shock that may be associated with capacitor use, but provides a vent path for gases that may be generated by the capacitor.
Yet another object of this invention is to provide a method of preventing electrical shock in association with dynamoelectric machine operation.
Still another object of this invention is to provide a modular replacement kit for use with dynamoelectric machines.